Slow start XJ - bought BMW part - where to install??

privatejoker said:
Someone told me that the ecm will not allow the engine to start until oil psi has reached a certain level. As clearances increase with age/mileage, cranking will take longer because it takes long to build up oil pressure. I know for a fact this is true with some vehicles, but what about jeeps?
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I've heard that about RENIX motors, but not the HOs. I actually don't know if RENIX motors can even monitor the pressure - it may just be a timed thing knowing that after X seconds it should be high enough.
 
5-90 could clarify this about the RENIX, but I know that the RENIX system has to rotate a certain amount in order to determine the position of #6 piston before it can start. A good strong battery/starter will help this along with a strong crank signal. The RENIX is a long cranker anyway but I'll try anything to help it out.

There is a BMW dealership in my nieghborhood, Im going to order that part. I just changed my pump and there was no check valve even on my assembly anywhere, someone else had removed it when the last pump was put in.
 
I have a question before I go and do this. Now I already let the fuel pump prime before cranking, but if I do this a couple of times and the engine starts quicker does that mean that getting the check valve will cure the problem. And what if I prime it a couple times and the start time doesn't get quicker, what does that mean.
 
TMXONR said:
I have a question before I go and do this. Now I already let the fuel pump prime before cranking, but if I do this a couple of times and the engine starts quicker does that mean that getting the check valve will cure the problem. And what if I prime it a couple times and the start time doesn't get quicker, what does that mean.
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I would say that if you prime multiple times and it starts quicker, then yes, the valve should help the situation, but I'm not going to say "cure". There are a lot of other factors including the fact that it's a 10-15yr old vehicle and they just don't start as fast as a new one. Also, I've heard that a new starter can make a fast improvement b/c they tend to wear over time - I just don't care enough to go that far. This $10 was well spent and saves me a few seconds per start.

As for a situation where priming doesn't help, I'd guess a new starter, possibly new battery or there's a faulty/bad sensor or connection to a sensor that is required for starting. It could also be that is just the way it's intended to be. Like I said, don't expect it to be a new car - mine still feels like a lifetime compared to my '07 Passat w/ pushstart - hell, I just push a button and it starts instantly. Guess the only way I can get the XJ to start that fast is to have someone w/ a Dodge Nitro jump start me while revving the engine...
 
Soo, I put in a BMW check valve and yet no results. Still takes a long time to start when warm. I'm thinking it's either the Fuel Pressure Regulator or the CPS. The only reason I'm not automatically assuming it's the CPS is because once started it acts like it's starving for fuel, then kicks right up to where it should be. If you were to shut it off, then get back to it within 10 mins, it fires right up. You would think that if the CPS was getting balky when warm, it would take the same amount of time to fire it up the second time?
 
Does anyone know if this does any good, I have considered putting a cold start valve and thermo time switch on mine, like on an '87 Volkswagen Golf. I also know the sync signal pickup is dead, so I want to try that first. You can unplug it and it just keeps running. What do ya'll think?
 
mrtosh said:
Soo, I put in a BMW check valve and yet no results. Still takes a long time to start when warm. I'm thinking it's either the Fuel Pressure Regulator or the CPS. The only reason I'm not automatically assuming it's the CPS is because once started it acts like it's starving for fuel, then kicks right up to where it should be. If you were to shut it off, then get back to it within 10 mins, it fires right up. You would think that if the CPS was getting balky when warm, it would take the same amount of time to fire it up the second time?
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Check the pressure itself at cold start, I've got a whiney pump and slowly increasing crank times, and occasionally a bit of stumble right when it fires and my main suspect is 100% fuel pump, this weekend I'm installing a pressure gauge. This is a stroker that has 100% new sensors 30k miles ago. and a 210k fuel pump.

In my experience electric fuel pumps don't just break (assuming you drive normally) they tend to wear down, build up resistance and operate poorly when they are cold and have been sitting. Which describes my symptoms perfectly,... in fact the engine starts nearly instantly when it's not cold. Basically every internal component of this engine is new/machined/balanced/toleranced or otherwise made like new 30k miles back so my "long crank" has nothing to do with tired internals or starter...
 
1bolt said:
Check the pressure itself at cold start, I've got a whiney pump and slowly increasing crank times, and occasionally a bit of stumble right when it fires and my main suspect is 100% fuel pump, this weekend I'm installing a pressure gauge. This is a stroker that has 100% new sensors 30k miles ago. and a 210k fuel pump.

In my experience electric fuel pumps don't just break (assuming you drive normally) they tend to wear down, build up resistance and operate poorly when they are cold and have been sitting. Which describes my symptoms perfectly,... in fact the engine starts nearly instantly when it's not cold. Basically every internal component of this engine is new/machined/balanced/toleranced or otherwise made like new 30k miles back so my "long crank" has nothing to do with tired internals or starter...
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That's the problem though, you listed that the fuel pump will act up when cold. mine always fires up immediatly in the mornings. Even w/it being 30 below out. Maybe the Fuel pressure regulator is bad,dk...
 
I've replaced every sensor/input/output device on my 90' RENIX has been replaced with dealer parts and it still is a long cranker. Really the only reason I replaced everything is due to the fact that this is a restoration project and I plan on driving it a long time. I would have bet that the check valve would have at least helped this problem, but seeing it didn't help yours...I'm not as sure now.

Here is a list of whats new;
TPS
CPS
MAT
CTS
IAC
injecters
distributer/synch sensor
coil/wires/plugs/module
knock sensor
Fuel pressure reg.
fuel filter
fuel pump
starter
altenator
battery cables
engine is rebuilt/head is reworked/intake and TB has been cleaned
pretty much everything else that I have forgotten has been replaced as well.

Still cranks as long as it has since 1990!
 
xjtrailrider said:
I've replaced every sensor/input/output device on my 90' RENIX has been replaced with dealer parts and it still is a long cranker. Really the only reason I replaced everything is due to the fact that this is a restoration project and I plan on driving it a long time. I would have bet that the check valve would have at least helped this problem, but seeing it didn't help yours...I'm not as sure now.

Here is a list of whats new;
TPS
CPS
MAT
CTS
IAC
injecters
distributer/synch sensor
coil/wires/plugs/module
knock sensor
Fuel pressure reg.
fuel filter
fuel pump
starter
altenator
battery cables
engine is rebuilt/head is reworked/intake and TB has been cleaned
pretty much everything else that I have forgotten has been replaced as well.

Still cranks as long as it has since 1990!
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I think it's still worth a try for you, seeing as how you've replaced just about everything else. I paid only $7.00 @the local BMW stealership. It comes w/everything you need to put it on(valve, fuel line, clamps.) Hopefully it works for ya....
 
FIXED!!! I changed the Fuel pressure Regulator this weekend and my problem is gone. No more long crank when warm.. The old FPR had a bunch of black crap in the screen. Guessing the diaphram was falling apart. Thanks for all the help guys... This forum rocks....
 
Air will get in the line, but I guess it just gets shot out during the first few cycles of the injectors. It's no different than changing a fuel filter and that's a standard practice.
 
on the older 87-90 4.0s with a long crank check the fuel presure regulator first. They fail in a way that lets all that presurized fuel get sucked in the intake by the vacuum line on the presure actuator. It loads up the the intake with way to much fuel.
 
ratman572 said:
Mine's a '91, so it might be different, but my pump runs for a couple of seconds when turning the switch to the "on" position. I noticed that I can cycle the key and get the pump to run for two times, -but never any more than twice. When I do cycle the key twice and let the pump run twice, my crank times are greatly reduced.

That leads me to believe that this check valve may very well reduce crank time.

The question is, -will it cause the injectors to weep?
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There may be differences, but on my '87 I was able to prime it like 4 times, before I tried to start. Would there be a problem since it let me prime so many times
 
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